Antimicrobial metallic copper surfaces kill Staphylococcus haemolyticus via membrane damage

Authors

Christophe Espirito Santo, 1.2
Davide Quaranta, University of Nebraska-LincolnFollow
Gregor Grass, University of Nebraska-Lincoln & Bundeswehr Institute of MicrobiologyFollow

Date of this Version

2012

Citation

MicrobiologyOpen 2012; 1(2): 46–52 doi: 10.1002/mbo3.2

Comments

2012 The Authors. MicrobiologyOpen published by Blackwell Publishing Ltd.

Abstract

Recently, copper (Cu) in its metallic form has regained interest for its antimicrobial properties. Use of metallic Cu surfaces in worldwide hospital trials resulted in remarkable reductions in surface contaminations. Yet, our understanding of why microbes are killed upon contact to the metal is still limited and different modes of action have been proposed. This knowledge, however, is crucial for sustained use of such surfaces in hospitals and other hygiene-sensitive areas. Here, we report on the molecular mechanisms by which the Gram-positive Staphylococcus haemolyticus is inactivated by metallic Cu. Staphylococcus haemolyticus was killed within minutes on Cu but not on stainless steel demonstrating the antimicrobial efficacy of metallic Cu. Inductively coupled plasma mass spectroscopy (ICP-MS) analysis and in vivo staining with Coppersensor-1 indicated that cells accumulated large amounts of Cu ions from metallic Cu surfaces contributing to lethal damage. Mutation rates of Cu- or steel-exposed cells were similarly low. Instead, live/dead staining indicated cell membrane damage in Cu- but not steel-exposed cells. These findings support a model of the cellular targets of metallic Cu toxicity in bacteria, which suggests that metallic Cu is not genotoxic and does not kill via DNA damage. In contrast, membranes constitute the likely Achilles’ heel of Cu surface-exposed cells.